Purpose: The diagnosis of early hepatic fibrosis, before it develops into cirrhosis, is crucial in patients with chronic liver disease, and allows for early treatment when the process may still be reversible. Compared to ultrasound-based elastography, MR elastography allows for evaluation of larger areas of the liver, and is being used in clinical practice. MR elastography sequences that have been validated by correlation to liver biopsy include gradient-echo (GRE) sequences, which sometimes yield a nondiagnostic scan, especially when iron deposition is present. Newer spin-echo (SE) echo-planar imaging (EPI) sequences have been developed and are proposed to allow for better stiffness evaluation. The purpose of the study was to compare the newer sequences to the traditional sequences, and evaluate whether SE-EPI sequences allow for evaluation of larger portions of the liver and whether the stiffness values measured on SE-EPI sequences are comparable to those measured on GRE sequences.
Materials and Methods: A retrospective single-center study was conducted, and included 35 consecutive patients with chronic liver disease related to various etiologies who underwent MR elastography with both GRE and SE-EPI sequences. Each sequence type was evaluated for the overall liver area that was visible for diagnosis, the liver area that yielded a diagnostic stiffness value and for the measured stiffness value.
Results: Statistical analysis was performed on 34 patients (1 was excluded because of giant hemangiomas). SE-EPI sequences had a higher rate of diagnostic scans than GRE sequences (100% vs. 94.1%), with a higher mean percentage of diagnostic slices (99.3% vs. 90.4%, p=0.026). SE-EPI sequences achieved a diagnostic stiffness value in a larger portion of the imaged liver (67.9% vs. 48.4%, p<0.001). Mean SE-EPI stiffness values were higher than GRE stiffness values by 0.37 kPa (4.697 kPa vs. 4.323 kPa).
Conclusion: SE-EP MR elastography sequences are able to image a larger portion of the liver at diagnostic quality, with a lower number of non-diagnostic scans. However, the difference in stiffness values compared with validated GRE sequences, although small, may cause incorrect fibrosis stage assignment. Therefore, further testing and validation of SE-EPI sequences is required before they can be entered into clinical use.
